Migrate from pkg/errors to standard library and enable depguard linter

[theyoprst]

Summary

Replace all usage of github.com/pkg/errors with Go's standard library error handling using fmt.Errorf() and the %w verb, and enable depguard linter to prevent future usage.

Part of #680. Closes #1001.

Changes Made

• Replaced all errors.Wrap(err, "message") with fmt.Errorf("message: %w", err)
• Removed github.com/pkg/errors imports from source files
• Added depguard linter configuration to prevent future pkg/errors usage
• Preserved standard library errors.New() usage where appropriate

Benefits

• Dependencies: Reduced external dependency footprint
• Future-proof: Linter enforcement prevents regression to deprecated patterns
• Compatibility: Better integration with Go 1.13+ error handling (errors.Is, errors.As)
• Standards: Aligns with modern Go development best practices

Breaking Changes

None. All error wrapping semantics are preserved through the %w verb.

[Copilot]

Pull Request Overview

This PR migrates error wrapping from pkg/errors to the Go standard library via fmt.Errorf() with the %w verb and enforces this pattern with a new depguard linter rule.

• Replaces pkg/errors.Wrap with fmt.Errorf(...) in numerous controller files
• Removes pkg/errors import and updates go.mod accordingly
• Adds a depguard linter configuration to prevent reintroduction of pkg/errors

Reviewed Changes

Copilot reviewed 39 out of 39 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
internal/controller/reconciler/k8s_job.go	Error wrapping updated using fmt.Errorf
internal/controller/reconciler/k8s_daemonset.go	Error wrapping updated using fmt.Errorf
internal/controller/reconciler/k8s_cronjob.go	Error wrapping updated using fmt.Errorf
internal/controller/reconciler/k8s_configmap.go	Error wrapping updated using fmt.Errorf
internal/controller/reconciler/grant.go	Error wrapping updated; note potential formatting inconsistency
internal/controller/reconciler/deployment.go	Error wrapping updated using fmt.Errorf
internal/controller/reconciler/apparmorprofile.go	Error wrapping updated using fmt.Errorf
internal/controller/clustercontroller/worker.go	Error wrapping updated using fmt.Errorf
internal/controller/clustercontroller/sconfigcontroller.go	Error wrapping updated using fmt.Errorf
internal/controller/clustercontroller/rest.go	Error wrapping updated using fmt.Errorf
internal/controller/clustercontroller/reconcile.go	Error wrapping updated using fmt.Errorf
internal/controller/clustercontroller/populate_job.go	Error wrapping updated using fmt.Errorf
internal/controller/clustercontroller/login.go	Error wrapping updated using fmt.Errorf
internal/controller/clustercontroller/exporter.go	Error wrapping updated using fmt.Errorf
internal/controller/clustercontroller/controller.go	Error wrapping updated using fmt.Errorf
internal/controller/clustercontroller/common.go	Error wrapping updated using fmt.Errorf
internal/controller/clustercontroller/benchmark.go	Error wrapping updated using fmt.Errorf
internal/controller/clustercontroller/accounting.go	Error wrapping updated using fmt.Errorf
go.mod	pkg/errors dependency removed and reordering updated
.golangci.yaml	depguard linter rule added to disallow pkg/errors

[theyoprst]

Thanks for the review! ✅ Fixed the formatting inconsistency.

Changes made:

• Removed extra spaces before colons in error messages across 4 files
• Now consistently using "message: %w" format instead of "message : %w"
• All error messages now follow the same formatting pattern

The fix has been included in the squashed commit 717aa11.